Flexible exothermic mat comprising particulate aluminum,binders and oxidizers

ABSTRACT

An exothermic charge is secured to a flexible backing material forming an elongated mat. Grooves in the mat extending from the surface of the charge to the backing material allow the mat to be placed over a regular shape such as a pipe to provide a covering blanket of exothermic charge. The flexible mat is particularly useful in combination with insulation and other accessories for exothermically annealing welded pipe and the like in the field.

United States Patent Bishop et al.

[ 1 Apr. 9, 1974 FLEXIBLE EXOTHERMIC MAT COMPRISING PARTICULATE ALUMINUM, BINDERS AND OXIDIZERS [75] Inventors: Harold F. Bishop; James R. Deck,

both of Conneaut, Ohio [73] Assignee: Exomet, Incorporated, Conneaut,

Ohio

[22] Filed: Mar. 16, 1973 [21] Appl. No.: 342,055

Related U.S. Application Data [62] Division of Ser. No. 163,722, July 19. 1971, Pat. No.

[52] U.S. Cl 149/15, 149/2, 149/37 [51 Int. Cl B23k 23/00 {58] Field of Search 102/103; 149/2, l5, 18,

[56] References Cited UNITED STATES PATENTS 3,067.686 12/1962 Coover, Jr. et al. 102/103 X 3,159,104 12/1964 Hodeson 102/103 3,176,618 4/1965 Forsberg et al.... 264/3 R 3,287,190 11/1966 Long 149/12 3,715,414 2/1973 Schultz et a1... 149/15 X 3,720,552 3/1973 Lustigue l49/l5 X Primary EmminerLeland A. Sebastian Attorney, Agent, or FirmBarry Moyerman; James C. Simmons 5 7 1 ABSTRACT 7 Claims, 4 Drawing Figures FLEXIBLE EXOTIIERMIC MAT COMPRISING PARTICULATE ALUMINUM, BINDERS AND OXIDIZERS This is a division, of application Ser. No. 163,722, filed July 19, 1971, now U.S. Pat. 3,751,308.

BACKGROUND OF THE INVENTION This invention pertains to heat treating of welded joints in structural elements by means of exothermic charges placed around the area to be treated. In the construction industry and in particular in construction of process plants employing many miles of pipe; the pipe is installed by welding successive lengths and joints such as tees, elbows, reducers, and the like at the construction site. Because the pipe sections are welded together, the welds and heat affected zones must be given a post-welding thermal treatment in order to reduce the residual stresses inherent in a weld where there was non-controlled cooling of the weldment. The type of post heat treatment depends upon the overall size, composition, and wall thickness of the welded sections and can be at a temperature either above or below the critical temperature. As a general rule the weld is heated to below the critical temperature for the metal composition, allowed to achieve temperature uniformity throughout the section being heated and then the temperature is gradually reduced to ambient. To a large extent the post-welding heat treatment, i.e., time, temperature and rate of cooling, are specified by industry and local building codes.

The most successful method of post-welding heat treatment of pipe and the like erected in the field is by an apparatus and method developed by Exomet, Inc. of Conneaut, Ohio, and marketed under the name EXO- ANNEAL. The EXO-ANNEAL apparatus consists of a kit containing shaped exothermic charges, insulation both high temperature and low temperature, insulating cement, sealing rings and fastening wires. Each kit is made up at the factory for a pre-ordered pipe size and can only be used on that size. The insulation and other components are selected and packed accordingly. In a large installation this requires a large number of kits to be in inventory to accommodate the varying pipe grades and sizes.

U.S. Pat. No. 3,192,080, is drawn to an exothermic heat treating apparatus and method also employing pre-shaped parts. This method has never been adopted because of the use of different exothermic sleeves in each unit or kit.

BRIEF DESCRIPTION OF THE INVENTION In order to avoid the above-mentioned problems with prior art exothermic heat treating devices and to provide an improved method and apparatus for exothermically treating weldments, it has been discovered that when the exothermic charge is affixed to a flexible backing or reenforcing in the form of a blanket or mat in a manner that allows shaping of the mat to regular surfaces in the field, and the mat combined with proper insulation can be used for many different sizes and grades of pipe and to provide a broad range of thermal treatments. The mat of exothermic material can be readily cut to the length and width desired in the field and shaped by hand because of apertures or grooves molded into the mat by the manufacturer. With this mat there is no need for large inventories of kits as the mat can be used at elbows, tees and the like.

Therefore, it is the primary object of this invention to provide a method and apparatus for post heat treatment of weldments.

It is another object of this invention to provide a flexible exothermic charge in the form of a mat.

It is still another object of this invention to provide a method for using a flexible exothermic charge in combination with insulation and fastening devices in order to accomplish controlled thermal treatment of a weldment.

BRIEF DESCRIPTION OF THE DRAWING DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing and in particular to FIGS.

1 and 2, there is shown a molded exothermic mat 10 of a composition within the followingbroad range:

Constituent Percent by Weight Fuel 15-30 Binder 3-10 Oxidizers 15-35 Flux 0.5-3.0 Refractory 25-40 In the above compositions the preferred fuel is finely divided aluminum in the form of 200 mesh (Tyler Standard Sieve Series) powder, grindings of mesh and chopped foil in the range of -20 to +200 mesh; the binder is starch, phenolic resin, natural sugars, synthetic sugars or mixtures thereof; the oxidizers are selected from the group consisting of manganese dioxide, red iron oxide (Fe O barium nitrate, sodium nitrate and mixtures thereof; the flux is cryolite; and the preferred refractory is ground fire brick in the size range of 20 to mesh.

In the above formula the aluminum foil and ground fire brick were found to have a particle size distribution as follows:

Tyler Sieve Size Percent Retained (mesh) Al Foil Brick -c tinued Distance Between Grooves l4 5/8 inches Width of Grooves 14 1/8 inches l yler Sieve Size Percent Rcluincd Depth of Grooves l4 [/2 inches (mesh) Al Foil Brick Distance Ccntcr Line of Grooves l6 2 inches Shape of Grooves l4, 16 "V" so 20 20 2'11 '2 5 p 2 The above dimensions are critical to the extent they have proven satisfactory for uses as will hereinafter be The exmhermlc mm l fvrmeq flcxlble described. The dimensions ofgrooves 16 are not necesbackmg l2 Q as a Screen fp of P sarily described because these grooves serve only as the proximately 1 The mat has a 5er1e$ f generally 10 means for determining the width of blanket to be used. parahel and equally Spaced grooves 14 disposed Referring now to FIGS. 3 and 4, there is shown a pipe pehdlcular to one edge of the mat It prefhrable 22 to elbow 24 connection by weld seam 26. In order h the mat 10 has a generally rectangular shape In top to relieve the stresses in the weld and surrounding base f so the grooves 14 are perpehdlcular to the long metal, exothermic mats 10', 10'', together with necesside of the rectangle. Grooves 14 extend from the top Sary accessories will be installed on the joint Surface 18 to the back'hg 12 and h a gene The first step is installation of a layer of thin flexible ally V-shaped cross section. A second series of grooves insulation 28 around the pipe 22 and elbow 26 where 16 (F 2) are prohded Perpehdcular to grooves the exothermic is to be placed. The insulation must These second grooves 16 are generally Parallel h overlap the weld according to the temperature desired other and eqhahy Spaced acros? the extehdmg as is specified for the pipe size and composition. Next depth m a pmht above the flhxlble back two layers of exothermic mat l0 and 10" are placed The purpose of grooves 14 to ahow the mat to over the insulation 28. The width of the mat is selected wrapped around a h 'h shrface such as a according to the temperature and in the case of a pipe the resuh that the uhlfohhly surrouhhed by to elbow, the thinner rings are added to assure uniform an exothermic mat or blanket. This is illustrated in FIG. heating of the entire heat affected area of the joint. 3 and will be more fully described hereinafter. Af the exothermic mats 10, 10" are in place they Grooves h provlded P that the mat 10 can be are covered with a 2-inch strip of heavier insulation 30, cut to varying widths for a given lengthover which is placed a final support wire 32. The insula- Mahufacture Ohthe h 10 f h h out 3 30 tion 30 is spaced about 4 inches apart on full width mold'hg prov'ded h prolect'ohs m the bottom mats and the wires 32 assure in situ reaction of the exocorresphhdmg to h requ'red gmqves After thermic composition. The voids between the mats are box g h h g f h f filled with a low temperature insulation 34, and the en- 0! er ac i therem'ht may e 5' tire assembly is covered with a composite outer insula- Z f K '2 35 tion 36 and secured in place with wires 38 (FIG. 3). F on the ace fl h t 8 h Additional low temperature insulation 40, 42 (FIG. 4) openings on surface 18, to aid in field installation ofthe is placed at the outer ends of the exothermic and blanket. After baking, the blanket is hard and relatively tened with wires (not shown) Insulation 40 42 is bnme so that can be handled and when requred mounted so that it can be moved away from the insulaformed to 9 40 tion in order to ignite the mats 10, 10'. After reaction Mats according to the present inventionare particuof the mats the insulation 40, 42 can be larly used for pipe sizes of four inches outside diameter moved against the mats in Order to control the cooling and larger. To accommodate this range of pipe sizes, of the entire assembly mats are made according to the following dimensions: Set forth in Examples are required items and Overall Length 30 inches Overall width 12 inches 45 sizes in order to accomplish exothermic post-welding Overall Thickness 7/8 inches heat treatment according to the present invention.

Example I 4" Schedule 40 or Standard Weight Pipe to Pipe Joint Stress Relieved at l 150 to l275F Item No. of Pieces Width Length Insulation 23 (.062" thick) I 6" 29 3/4" Exothermic Mat 10 l 6" 18 1/4" Exothermic Mat 10 l 6" 23 1 2" insulating Strips 3O 2 2" 29" Insulation 36 l 7" 36" Insulation 42 2 [6 2l Example ll 4" Schedule or extra heavy Pipe to Pipe Joint Stress Relieved at 1350 to 1475F Item No. of Pieces Width Length Insulation 28 (.062"thick) 1 l4" 29 3/4" Exothermic Mat 10' 1 l4" l8 l/4 Exothermic Mat 10" 1 14" 23 H2" insulating Strips 3O 4 2" 29" Insulation 36 1 I5" 36" Insulation 72 2 l6" 2]" Example III I"Schedule 20 Pipe to Pipe Joint Anneal at 1550 to l650F Item No. of Pieces Width Length Insulation 38 (.O62"thick) l 18" 34" Exothermic Mat I0 I I8" 36 /8" Exothermic Mat I I8" 42 3/4" Exothermic Mat I I8" 48 1/4" Insulating Strips 3O 5 2" 5S" Insulation 36 I I9" 70" Insulation 42 2 4 Sealing Insulation 2 4" 53" Third mat placed over mat l0" in same manner as described. Placed at the joint of insulation 36 and 42 covering insulation 42.

Example IV 20" Schedule pipe to pipe joint 1150 to I275F stress relieve treatment Item No. of Pieces Width Length Insulation 28 (023" thick) 1 24" 63" Exothermic Mat l0 1 24" 65 3/4" Exothermic Mat I0" I 24" 71" Insulating Strips 3O 8 2" 75" Insulation 36 l 15" 94" Insulation 42 2 16" 70" In the above examples, insulation 28 is an asbestos paper having an asbestos fiber content of 99 percent and is sold by Johns-Manville as asbestos welding paper. The insulating strips 30 are 54 inch thick and are prepared, commercially available, white insulating asbestos. They serve to prevent burn through of wires 32 during reaction of the exothermic charge. In place of wire 32 regular commercial metal banding or strapping can be used. Insulation 36 is a composite consisting of asbestos welding paper next to the exothermic mat; to this is fastened an alumina-silica fiberous insulation about /2 inch thick having a density of 8 pounds per cubic foot and is sold under the tradename CERA- FELT by Johns-Manville; this is covered by a layer of mineral fiber blanket 2 inches thick having a density of 8 pounds per cubic foot, sold by Eagle-Picher Industries, Inc. under the tradename SUPERGLAS. The insulation 42 and sealing insulation of Example III are made from the same mineral fiber as the outer 2 inches of insulation 36.

From the above examples it can be seen that the apparatus and method of the instant invention is applicable to an infinite variety of exothermic heat treating problems. The method can be tailored to fit the pipe size, shape, composition, joint and atmospheric conditions to satisfy all weld treating codes. In the matter of insulation this can be varied to accomplish longer or shorter post heating cooldown depending upon the material.

Flexible exothermic mats and accessories according to the present invention can also be used to pre-heat pipe sections prior to welding as well as for other routing maintenance work in the field.

The exothermic can be manufactured on a plastic, paper. cardboard, thin foil, carpet or other flexible backing that may or may not be within the exothermic. Once the exothermic is in place, the backing has really served its purpose. The primary purpose of the perforated back is to provide structural strength to the exothermic mat and to allow cutting of the mat to the proper length and width without unnecessary crumbling of the exothermic.

Having thus described our invention, the following is desired to be secured by Letters Patent of the United States.

We claim:

1. A flexible exothermic material suitable for field heat treating of welded pipe, and the like, comprising:

a flexible backing;

an exothermic charge secured to said backing, said charge consisting of 15 to 30 percent by weight fuel selected from the group consisting of 200 mesh aluminum powder, mesh aluminum grinding and 20 to +200 mesh aluminum foil, 3 to 10 percent by weight binder selected from the group consisting of starch, phenolic resin, natural sugars, synthetic sugars or mixtures thereof, 15 to 35 percent by weight oxidizer selected from the group consisting of manganese dioxide, red iron oxide (Fe O barium nitrate, sodium nitrate and mixtures thereof; 0.5 to 3 percent by weight flux, and 25 to 40 percent by weight refractory having a particle size of -20 to mesh; and series of grooves in said exothermic charge generally parallel to and uniformly spaced one from the other, said grooves extending from one surface of the exothermic toward the backing material to an effective depth; whereby the backing material and exothermic may be readily shaped to a regular shaped contour.

2. An exothermic material accdFdih'fiJihilh 1 wherein the grooves are in the shape of an inverted triangle.

3. An exothermic material according to claim 1 wherein there are a plurality of parallel grooves uniformly spaced from each other and generally perpendicular to the first series of grooves.

4. An exothermic material according to claim 1 wherein the backing material is a wire screen of a mesh size of greater than one-eighth inch.

5. An exothermic material according to claim 1 7. An exothermic material according to claim 1 wherein the exothermic charge is approximately 19.4 percent by weight finely divided aluminum, 8.6 percent by weight phenolic resin, 34 percent by weight red iron oxide (Fe o l.7 percent by weight flux and 36.3 percent by weight refractory. 

2. An exothermic material according to claim 1 wherein the grooves are in the shape of an inverted triangle.
 3. An exothermic material according to claim 1 wherein there are a plurality of parallel grooves uniformly spaced from each other and generally perpendicular to the first series of grooves.
 4. An exothermic material according to claim 1 wherein the backing material is a wire screen of a mesh size of greater than one-eighth inch.
 5. An exothermic material according to claim 1 wherein the backing material is selected from the group consisting of kraft paper, cloth, plastic sheeting, cardboard, a plurality of parallel elongate flexible rods, and carpet backing.
 6. An exothermic material according to claim 1 wherein the flux is cryolite and the refractory is ground fire brick.
 7. An exothermic material according to claim 1 wherein the exothermic charge is approximately 19.4 percent by weight finely divided aluminum, 8.6 percent by weight phenolic resin, 34 percent by weight red iron oxide (Fe2O3), 1.7 percent by weight flux and 36.3 percent by weight refractory. 